The present invention relates to a guide shoe for sliding within a rail of U-shaped cross-section. It has particular application to a guide shoe for a sliding roof of a vehicle, which shoe is connected with a slidable part of the vehicle roof and is guided within a rail having a U-shaped cross-section.
Said guide shoes must be constructed in such a way that over a long period of time they are guided in their rails with as little lateral movement as possible in order to avoid rattling of the said slidable part. In addition, there must be minimum friction of the guide shoes in their rails. Various guide shoe constructions are known for the fulfillment of these requirements, but each of these has certain disadvantages. The guide shoe described in German Pat. No. 1,111,962 is made from plastics material and is constructed in such a way that its ends engage resiliently in the guide rails. The plastics material used must be relatively hard in order to ensure engagement of the guide shoe with the rail surfaces with a force which is such that even in the case of the powerful impacts which the vehicle occasionally suffers, rattling of the sliding roof is prevented. As a result of the material hardness, relatively narrow tolerances must be provided both for the guide shoe and for the guide rail. There is also the danger that after a not particularly long period, the material will be subject to fatigue and lose the necessary tension. To avoid this, a guide shoe according to German Auslegeschrift No. 1,630,330 (U.S. Pat. No. 3,558,183) uses a plastics body in which is embedded a metallic spring. Due to the metallic spring, this guide shoe maintains its elasticity over a longer period and, due to the plastics body, has good sliding characteristics. However, as a result of pressure on the springs, this guide shoe may rise from a sliding surface, resulting in the loss of the precise guidance in the vertical direction and the occurrence of rattling. In addition, this guide shoe has the disadvantage of relatively high manufacturing costs.
The present invention contemplates providing a guide shoe, which is characterized by simple construction and ease of manufacture and which permits larger tolerances of the guide rail in both vertical and horizontal directions.
According to the invention, the guide shoe is made from an elastically deformable material, e.g. a rubber, and a friction reducing support on its sliding surfaces is provided.
The use of an elastically deformable material permits the guide shoe to be constructed in such a way that it can always be inserted into the guide rail with an initial stress, i.e. accompanied by compression. This compensates for relatively large tolerance fluctuations in the spacings of the legs of the guide rail. Moreover, the guide shoe according to the invention also compensates for the tolerances in the horizontal direction, i.e. differences in the spacing between the crosspieces of two guide rails fitted to the opposed lateral edges of the roof opening, because said crosspieces serve to guide the slidable roof part in the horizontal direction, i.e. for centering relative to the roof opening. This problem has not hitherto been tackled. Thus, the term "sliding surfaces" is understood to mean not only the peripheral surfaces of the guide shoe sliding on the inner surfaces of the legs of the U-shaped rail, but also the rear surfaces of the guide shoe which cooperate with the inner surface of the crosspiece of the U-section.
In preferred embodiments, the support is made from a backed foil, e.g. of polytetrafluoroethylene or a similar material with good sliding characteristics.
However, the support can also comprise a coating of a slidable material, e.g. polyamide, in accordance with other preferred embodiments of the invention.
The present invention also contemplates embodiments with the sliding surfaces covered with fibers of a slidable material; for example polyamide fibers.
In order to reduce the contact surface of the guide shoe on the rail, the sliding surfaces are preferably formed by projections from the main body of the shoe.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in conjunction with the accompanying drawings which show, for purposes of illustration only, a single embodiment in accordance with the present invention.